Liquid crystal module with tab assemblies connected through a flexible circuit board

ABSTRACT

A matrix liquid crystal unit having a liquid crystal panel composed of two flexible plastic substrates and a liquid crystal material sandwiched between the flexible plastic substrates, and a flexible circuit sheet with a plurality of liquid crystal driver TAB·LSI assemblies mounted thereon are electrically connected to each other, making up a liquid crystal unit. Each of the flexible plastic substrates has a group of liquid crystal driver electrodes. Each of the liquid crystal driver TAB·LSI assemblies has a group of output terminals connected respectively to the liquid crystal driver electrodes through connection lines on the flexible circuit sheet. A connector connected to electrode terminals on the flexible circuit sheet, an interface connector to be connected to electrode terminals of an external control device, and printed wires for electrically connecting the connectors to each other, jointly make up a thin board. A liquid crystal module is composed of the liquid crystal unit and the thin board which are superimposed one on the other.

DESCRIPTION

1. Technical Field

The present invention relates to an ultrathin and ultralightweightliquid crystal module which can freely be bent without causing troublessuch as wiring breaks, and which has a liquid crystal panel and a boardthat can be replaced easily.

2. Background Art

As shown in FIG. 16 of the accompanying drawings, one conventionalliquid crystal panel comprises a liquid crystal 201 sandwiched between apair of glass substrates 200. The liquid crystal panel also has a groupof liquid crystal drive electrodes (not shown) disposed on each of theglass substrates 200. These liquid crystal drive electrodes areconnected to liquid crystal driver LSI circuits 203 through a connectioncircuit network on a printed circuit board 202.

Since the conventional liquid crystal panel is composed of glasssubstrates and a relatively hard printed circuit board, the entireassembly has been inflexible, rigid, and flat.

Large-size liquid crystal panels which incorporate glass substrates areconsiderably heavy. Therefore, it is necessary to install suchlarge-size liquid crystal panels stably so that they will not bedeformed and will be resistant to vibrations. A lot of labor is requiredto assemble and maintain the large-size liquid crystal panels, resultingin a great total cost which has made the large-size liquid crystalpanels impracticable and prevented them from finding wide use.

In recent years, there have been developed various liquid crystal panelswhich have flexible plastic substrates and hence are lightweight and canbe flexed, providing curved surfaces (see Japanese patent publicationNo. 1-6084 and Japanese laid-open patent publication No. 1-91113) .

In such a liquid crystal panel with flexible plastic substrate, however,it is not possible to mount a printed-circuit board directly on aplastic substrate. It is therefore necessary to use a liquid crystaldriver LSI circuit and an interconnection network as external circuits,around or independently separately from the liquid crystal panel. As aresult, the liquid crystal display device incorporating the liquidcrystal panel has large outer dimensions.

There is also known a liquid crystal display device including a liquidcrystal panel that has flexible plastic substrates, and circuits such asa liquid crystal driver LSI circuit mounted on the reverse side of theliquid crystal panel through a reinforcing plate and a circuit boardthat can be bent to a certain extent.

With the known liquid crystal display device, configurations that theliquid crystal panel can take are governed by the rigidity and shape ofthe reinforcing plate and the circuit board which are disposed on thereverse side of the liquid crystal panel. Thus, the flexibility of theplastic substrates cannot fully be utilized, so that the liquid crystaldisplay device displays desired information in a limited curvaturerange.

Another problem is that the weight and thickness of the liquid crystalpanel are increased by the reinforcing plate and other components.

Since the circuit board and the liquid crystal driver LSI circuit arefixed to the liquid crystal panel, when the liquid crystal panel isdeformed, stresses are developed in joints between terminals of liquidcrystal driver electrodes on the plastic substrates and interconnectionsof the liquid crystal driver LSI circuit, tending to cause defects suchas wiring breaks and peeling of the liquid crystal panel. In order toavoid such defects, the shape of the liquid crystal panel cannot bechanged after it has been determined once.

The circuit board terminals and external input terminals are generallyjoined by soldering or the like. Therefore, when a defect occurs afterthe liquid crystal panel has been packaged, it is difficult to replaceand reuse the liquid crystal panel and the circuit board, resulting in areduced yield.

Prior liquid crystal display devices are designed such that a liquidcrystal display unit is relatively large in size and an electroniccircuit for driving the liquid crystal is as compact as possible formaking the liquid crystal devices thin and light. To fabricate thin andlight liquid crystal display devices, there is employed a TAB·LSIarrangement in which leads are formed on a tape-like film and a liquidcrystal driver LSI is mounted on the film by TAB (Tape AutomatedBonding).

Different methods of mounting a TAB·LSI arrangement or assembly on aliquid crystal panel are known in the art. According to one mountingmethod, the output terminals of the TAB·LSI assembly are directlyconnected to the output terminals of liquid crystal driver electrodesformed on glass substrates of a liquid crystal panel. Another mountingprocess employs a flexible printed circuit board (FPC) through which theoutput terminals of the TAB·LSI assembly are connected to the outputterminals of liquid crystal driver electrodes. The terminals areconnected by thermocompression bonding with an anisotropic conductiveadhesive.

In liquid crystal display devices with TAB·LSI assemblies, the glasssubstrates and the base film or FPC board have different coefficients ofthermal expansion because they are made of different materials.Therefore, when the terminals are cooled after they have been connectedby thermocompression bonding, the joints between the glass substratesand the base film or FPC are subject to residual stresses arising fromdifferent degrees of shrinkage of the glass substrates and the base filmor FPC board.

More specifically, the coefficient of thermal expansion of the glasssubstrates is about 4.0×10⁻⁶ (cm/cm/°C.), and the coefficient of thermalexpansion of the base film or FPC is about 3˜7×10⁻⁵ (cm/cm/°C.). Asthese coefficients of thermal expansion differ greatly from each other,any residual stresses applied to the electric joints between the glasssubstrates and the base film or FPC are large, tending to cause wiringbreaks or other defects.

The terminals of the liquid crystal driver electrodes and the outputterminals of the TAB·LSI assembly are closely spaced at small pitchesand have small contact areas. Therefore, these terminals are liable toget peeled off easily, resulting in wiring breaks.

In order to solve the problem of the peeling of the terminals due to thedifferent coefficients of thermal expansion, it has been known in theart to use a fastener to secure the terminals as disclosed in Japaneselaid-open patent publication No. 2-214823, or to form the electrodeterminals of the TAB·LSI assembly as projecting from the base film asdisclosed in Japanese laid-open utility model publication No. 63-70149.

The proposal disclosed in Japanese laid-open patent publication No.2-214823 has a problem in that the liquid crystal panel becomes thickerand heavier because of the fastener. The disclosure of Japaneselaid-open utility model publication No. 63-70149 is disadvantageous inthat the projecting electrode terminals are apt to be damaged or broken.Therefore, either one of the disclosed arrangements has provenunsatisfactory.

Therefore, it is an object of the present invention to provide a liquidcrystal module which is free of the shortcomings of the conventionalliquid crystal display devices, i.e., which is flexible, ultrathin andultralightweight, and allows a liquid crystal panel and a circuit board(sheet) to be replaced easily.

Another object of the present invention is to provide a liquid crystalmodule which allows a liquid crystal panel to be bent freely withoutcausing troubles such as wiring breaks or the like.

DISCLOSURE OF THE INVENTION

A liquid crystal module according to the present invention comprises amatrix liquid crystal unit having a liquid crystal panel composed of twoflexible plastic substrates and a liquid crystal material sandwichedbetween the flexible plastic substrates, and a flexible circuit sheet(FPC) with a plurality of liquid crystal driver TAB·LSI assembliesmounted thereon, and a thin board composed of a connector connected toelectrode terminals on said flexible circuit sheet, an interfaceconnector to be connected to electrode terminals of an external controldevice, and printed wires for electrically connecting the connectors toeach other, the matrix liquid crystal and the thin board being of anintegral construction. Preferably, all of the liquid crystal driverTAB·LSI assemblies are mounted as a whole on a flat surface of theflexible circuit sheet.

The liquid crystal module thus constructed is flexible,ultralightweight, and ultrathin, allowing the liquid crystal panel andthe circuit sheet to be replaced easily.

A liquid crystal module further according to the present inventioncomprises at least a liquid crystal panel having two flexible plasticsubstrates and a liquid crystal material sandwiched between the flexibleplastic substrates, and a plurality of liquid crystal driver TAB·LSIassemblies, each of said flexible plastic substrates having a group ofliquid crystal driver electrodes mounted thereon, each of said liquidcrystal driver TAB·LSI assemblies having a group of output terminalsconnected respectively to said liquid crystal driver electrodes.

Also according to the present invention, a liquid crystal modulecomprises at least a liquid crystal panel having two flexible plasticsubstrates and a liquid crystal material sandwiched between the flexibleplastic substrates, a plurality of liquid crystal driver TAB·LSIassemblies, and a flexible circuit sheet having connection lines formedthereon, each of said flexible plastic substrates having a group ofliquid crystal driver electrodes mounted thereon, each of said liquidcrystal driver TAB·LSI assemblies having a group of output terminalsconnected respectively to said liquid crystal driver electrodes throughsaid connection lines on said flexible circuit sheet.

The liquid crystal panel of the liquid crystal module can freely be bentwithout causing troubles such as wiring breaks or the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a liquid crystal displayincluding a liquid crystal module according to a first embodiment of thepresent invention;

FIG. 2 is an exploded perspective view of the liquid crystal moduleaccording to the first embodiment of the present invention;

FIG. 3 is a plan view of a liquid crystal driver TAB-mounted flexiblecircuit sheet for the liquid crystal module according to the firstembodiment of the present invention;

FIG. 4 is a plan view of a liquid crystal driver TAB circuit for theliquid crystal module according to the first embodiment of the presentinvention;

FIG. 5 is a plan view showing a wiring pattern on the face side of acircuit sheet of the liquid crystal module according to the firstembodiment of the present invention;

FIG. 6 is a plan view showing a wiring pattern on the reverse side of acircuit sheet of the liquid crystal module according to the firstembodiment of the present invention;

FIG. 7 is a plan view of a thin board of the liquid crystal moduleaccording to the first embodiment of the present invention;

FIG. 8 is a view showing an entire wiring system of the liquid crystalmodule according to the first embodiment of the present invention;

FIG. 9(a) is a perspective view of one specific arrangement of a liquidcrystal module according to a second embodiment of the presentinvention;

FIGS. 9(b) and 9(c) are cross-sectional views of the specificarrangement shown in FIG. 9(a);

FIG. 10 is a plan view of a liquid crystal driver TAB·LSI assembly ofthe specific arrangement shown in FIG. 9 (a);

FIG. 11 (a) is a plan view of another specific arrangement of the liquidcrystal module according to the second embodiment of the presentinvention;

FIGS. 11 (b) and 11 (c) are cross-sectional views of the other specificarrangement shown in FIG. 11 (a);

FIG. 12 is a fragmentary cross-sectional view of a liquid crystal panelwith polarizers and a reflector in the other specific arrangement of theliquid crystal module;

FIG. 13 is a perspective view showing a liquid crystal panel bezel and acontrol circuit of the other specific arrangement of the liquid crystalmodule;

FIGS. 14(a) and 14(b) are perspective views showing bent and flatconditions of the liquid crystal panel according to the secondembodiment of the present invention;

FIG. 15(a) is a plan view of still another specific arrangement of theliquid crystal module according to the second embodiment of the presentinvention;

FIGS. 15(b) and 15(c) are cross-sectional views of the still otherspecific arrangement shown in FIG. 15(a); and

FIG. 16 is a perspective view of a conventional liquid crystal displaydevice.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described in detail with reference to theaccompanying drawings.

A first embodiment of the present invention will first be described withreference to FIGS. 1 through 8.

FIG. 1 is an exploded perspective view of a liquid crystal displayincluding a liquid crystal module according to the first embodiment ofthe present invention, and FIG. 2 is an exploded perspective view of theliquid crystal module according to the first embodiment of the presentinvention.

As shown in FIG. 1, a liquid crystal module 1 according to the firstembodiment is housed in an outer casing comprising a front panel 101 anda rear panel 102, and the entire assembly is used as a liquid crystaldisplay.

The liquid crystal module 1 comprises a liquid crystal unit 80 which hasa liquid crystal panel unit 10 having at least a liquid crystal paneland a circuit unit 20 having at least a flexible circuit sheet (FPC),the liquid crystal panel unit 10 and the circuit unit 20 being connectedto each other, and a thin board 60.

As shown in FIG. 2, the liquid crystal panel unit 10 comprises a liquidcrystal panel 11 composed of a liquid crystal sandwiched between twothin flexible plastic substrates, a polarizing filter 12 disposed on theface side (front surface) of the liquid crystal panel 11, a polarizingfilter 13 and a reflector 14 which are disposed on the reverse side ofthe liquid crystal panel 11. The liquid crystal panel 11, the polarizingfilters 12, 13, and the reflector 14 are superimposed without clearancestherebetween.

Although not shown in FIG. 2, each of the flexible plastic substrates ofthe liquid crystal panel 11 has a group of liquid crystal driverelectrodes on its surface sandwiching the liquid crystal. The liquidcrystal driver electrodes include segment electrodes on one of theflexible plastic substrates and common electrodes on the other flexibleplastic substrate. The liquid crystal panel 11 is therefore of thematrix display type.

The flexible plastic substrates may be made of a crystalline polymersuch as uniaxially or biaxially oriented polyethylene terephthalate, anon-crystalline polymer such as polysulfone, polyether sulfone, orpolycarbonate, a polyolefin such as polyethylene or polypropylene, apolyamide such as nylon. Of these materials, particularly preferable areuniaxially or biaxially oriented polyethylene terephthalate andpolyether sulfone.

The two flexible plastic substrates may be of the same material ordifferent materials. Normally, at least one of the flexible plasticsubstrates is optically transparent, with transparent electrodes mountedthereon.

The flexible plastic substrates should have a thickness of 0.3 mm orless each. If the thickness of the flexible plastic substrates exceeds0.3 mm, they only allow the liquid crystal panel 11 to be deformed tolarge curvatures. As the thickness of the flexible plastic substrates isreduced, the flexible plastic substrates can be deformed freely to smalland large curvatures. Preferably, the thickness of the flexible plasticsubstrates should range from 20 to 100 μm. The flexible plasticsubstrates in such a thickness range may be referred to as flexiblefilms.

The liquid crystal driver electrodes on the flexible plastic substratesmay be made of any materials insofar as they are electricallyconductive. However, the electrodes in at least one of the groups shouldpreferably be made of a material that is both electrically conductiveand transparent. Specifically, those electrodes may comprise transparentelectrodes made of indium oxide or ITO (Indium Tin Oxide) which is amixture of indium oxide and tin oxide.

The liquid crystal driver electrodes may be formed on the flexibleplastic substrates by any known process such as evaporation, sputtering,or the like.

The liquid crystal sandwiched between the flexible plastic substrates isnot limited to any materials, but should preferably be made of aferroelectric liquid crystal material, for example, a ferroelectricliquid crystalline polymer or a composition thereof.

The ferroelectric liquid crystal may be a ferroelectric low-molecularweight liquid crystal (monomeric liquid crystal), a ferroelectric liquidcrystalline polymer, or their mixture.

The ferroelectric low-molecular weight liquid crystal may, for example,be one or more ferroelectric low-molecular weight liquid crystals, or aferroelectric low-molecular weight liquid crystal which comprises amixture of one or more ferroelectric low-molecular weight liquidcrystals and another low-molecular weight liquid crystal.

The ferroelectric liquid crystalline polymer polymers, or aferroelectric liquid crystalline polymer which comprises one or moreferroelectric low-molecular weight liquid crystals and one or moreferroelectric liquid crystalline polymers, or a ferroelectric liquidcrystalline polymer which comprises one or more ferroelectriclow-molecular weight liquid crystals and one or more other liquidcrystalline polymers.

More specifically, the ferroelectric liquid crystalline polymer may beany of all liquid crystalline polymers which exhibit the ferroelectricproperty, e.g., a ferroelectric liquid crystalline polymer (ahomopolymer, or a copolymer, or a mixture thereof) whose polymermolecules exhibit ferroelectric liquid crystal characteristics, or amixture of a ferroelectric liquid crystalline polymer and another liquidcrystalline polymer and/or an ordinary polymer, or a mixture of aferroelectric liquid crystalline polymer and a ferroelectriclow-molecular weight liquid crystal, a mixture of a ferroelectric liquidcrystalline polymer, a ferroelectric low-molecular weight liquidcrystal, a liquid crystalline polymer and/or an ordinary polymer, or amixture of any of the above liquid crystal or mixtures and an ordinarylow-molecular weight liquid crystal.

Particularly referable of the above ferroelectric liquid crystallinepolymers is a side-chain ferroelectric liquid crystalline polymer inchiral smectic C phase, for example.

Examples of the ferroelectric liquid crystalline polymeric compounds aredecyloxy-benzylidene-P'-amino-2-methylbutyl-cinnamate (DOBAMBC),hexyloxy-benzylidene-P'-amino-2-chloropropyl-cinnamate (HOBACPC), and4-o-(2-methyl)-butylresorcylidene-4'-octylaniline (MBRA8).

When the liquid crystal panel is constructed of the above materials, itis kept at such a temperature that the liquid crystal compound will bein SmC* phase or SmH* phase. If necessary, the liquid crystal panel maybe supported on a copper block or the like in which a heater isembedded.

According to the present invention, it is also possible to use aferroelectric liquid crystal in chiral smectic F phase, I phase, Jphase, G phase, or K phase, other than SmC* phase or SmH* phase.

The ferroelectric liquid crystal composition may contain an adhesive, aviscosity reducer, a non-liquid-crystal chiral compound, a dye, etc. Thethickness of the liquid crystal layer should preferably, but notnecessarily, be in the range of from 2 to 4 μm.

From the viewpoint of providing a liquid crystal panel having a largedisplay area, flexibility, a lightweight, and a thin profile, it ispreferable to use a ferroelectric liquid crystalline polymer among otherferroelectric liquid crystal materials.

The polarizing filters 12, 13 are generally made of a polyvinyl alcohol(PVA)--iodine material, or a PVA--material. The polarizing filters 12,13 should preferably be flexible, and hence should preferably of athickness of 0.2 mm or less.

The polarizing filters 12, 13 are disposed on the face and reversesides, respectively, of the liquid crystal panel 11 in crossed nicols.If a guest-host liquid crystal is used, then the polarizing filters aredisposed on the face side (display side) of the liquid crystal, or theopposite side (reverse side) thereof. In any case, the polarizingfilters 12, 13 are bonded to the flexible plastic substrates such thatthe contrast ratio achieved when the electric field is turned on and offis maximum.

The reflector 14 is positioned on the reverse side (non-display side) ofthe liquid crystal panel. The reflector 14 may be a metal foil ofaluminum (Al), a sheet composed of a metal foil and a resin film bondedthereto, or the like. The reflector 14 should preferably be of athickness of 0.2 mm or less.

If a backlight is employed in place of the reflector, then the liquidcrystal panel is of the transmission type.

A color film (color filter) 15 and a protective plate 16 are positionedin front of the liquid crystal panel 10. The color-film 15 is used toadjust the color tone, and the protective plate 16 is used to give theliquid crystal panel 10 a safety strength required in the use.

As shown in FIG. 3, the circuit unit 20 comprises a flexible circuitsheet (FPC) 21 with a plurality of liquid crystal driver TAB·LSIassemblies (described later on) 50A, 50B, and insulation sheets 22, 23superimposed on the respective opposite surfaces of the flexible circuitsheet 21.

The flexible circuit sheet 21 comprises, as shown in FIG. 3, a polyesterfilm having a thickness of 25 with printed wires on its face and reversesides, two TAB·LSI assemblies 50A, 50B for driving the commonelectrodes, and one TAB·LSI assembly 50C for driving the segmentelectrodes, the TAB·LSI assemblies 50A, 50B, 50C being mounted flatwiseon the polyester film. The flexible circuit sheet 21 serves to drive thecommon and segment electrodes of the liquid crystal panel describedabove.

The printed wires on the face and reverse sides of the flexible circuitsheet 21 are connected via through holes. The face and reverse sides ofthe flexible circuit sheet 21 are electrically insulated from externalcomponents by the insulation sheets 22, 23 superimposed on the face andreverse sides of the flexible circuit sheet 21.

The flexible circuit sheet 21 should preferably be composed of apolyester film or polyimide film which is highly soft andheat-resistant. The thickness of the flexible circuit sheet 21 shouldpreferably be of 0.1 mm or smaller.

The printed wires (as a conductive layer) may be made of anyelectrically conductive material. However, in order to prevent them frombeing broken even when a wiring sheet is folded over, the printed wiresshould preferably be made of electrically conductive particles ofsilver, graphite, metal, or their blend, dispersed in a flexiblepolymeric resin binder. The printed wires may be produced by screenprinting, photolithography, or the like.

The flexible circuit sheet 21 should preferably be disposed on the backof the liquid crystal panel 11 in order to be able to increase theproportion of the display area with respect to the liquid crystalmodule.

As shown in FIG. 4, each of the liquid crystal driver TAB·LSI assemblies50A, 50B, 50C, collectively referred to as "TAB·LSI assembly 50"comprises a base film 51 in the shape of a tape with sprocket holes,leads 52a, 52b formed on the base film 51, and LSI circuits 53 mountedon the base film 51 and connected to the leads 52a, 52b by TAB (TapeAutomated Bonding). Such an assembly is referred to as a TAB·LSIassembly. The TAB·LSI assembly 50 is distinct from an ordinary LSIcircuit which is mounted on a lead frame by wire bonding.

The TAB·LSI assembly should preferably be of a thickness of 1 mm orless.

The base film 51 on which the LSI circuit is mounted comprises apolyimide or polyester (PET) film which is highly soft andheat-resistant. Output terminals 53a are connected to the respectivedistal ends of the leads 52a, and input terminals 53b are connected tothe respective distal ends of the leads 52b.

There are 160 output terminals 53a and 34 input terminals 53b.

The flexible circuit sheet 21 has printed wires on its face side asshown in FIG. 5. In FIG. 5, the flexible circuit sheet 21 supports onits upper end 288 segment-side electrode terminals 30 and on itsrighthand end 96 common-side electrode terminals 31. These segment-sideelectrode terminals 30 and common-side electrode terminals 31 jointlyserve as liquid crystal driver electrodes.

Of the 288 segment-side electrodes 30, 160 electrodes positioned on thelefthand side are driven by the TAB·LSI assembly 50A (whose all 160electrodes are employed) through printed wires 32A, and remaining 128electrodes positioned on the righthand side are driven by the TAB·LSIassembly 50B (whose 128 out of 160 electrodes are employed) throughprinted wires 32B.

Likewise, the 96 common-side electrodes 31 are driven by the TAB·LSIassembly 50C (whose 96 out of 160 electrodes are employed) throughprinted wires 32C. The printed wires 32A˜32C have ends arranged asheat-sealing connectors 33A˜33C, respectively, which can be connected tothe output terminals 53a of the TAB·LSI assemblies by thermalcompression. Specifically, hot-melt resin layers are coated as adhesivelayers on the printed wires for connection to the output terminals 53aof the TAB·LSI assemblies by thermal compression.

The face side of the flexible circuit sheet 21 also has printed wires34A˜34C to be connected to the input terminals 53b of the TAB·LSIassemblies 50A˜50C as shown in FIG. 4. The printed wires 34A˜34C haveends arranged as heat-sealing connectors 35A˜35C, respectively, whichcan be connected to the input terminals 53b of the TAB·LSI assemblies bythermal compression.

The printed wires 34A˜34C are connected to printed wires (describedlater on) on the reverse side of the flexible circuit sheet 21 viathrough holes 36A˜36C. The printed wires on the reverse side are joinedvia through holes 37 to input/output buses 38 on the face side of theflexible circuit sheet 21, which are connected to 26 input-sideelectrode terminals 39 that are connected to a lock connector 61 of thethin board 60.

The input-side electrode terminals 39 are lined with a thin plasticreinforcing plate, providing a thickness of about 0.3 mm, as only theflexible sheet (which is 25 μm thick) has too small mechanical strength.

FIG. 6 shows a circuit pattern on the reverse side of the flexiblecircuit sheet 21.

The input terminals of the TAB·LSI assemblies 50A, 50B on the face sideof the flexible circuit sheet 21 are connected via the through holes36A, 36B to 34 segment-side common buses 40. Similarly, the inputterminals of the TAB·LSI assembly 50C on the face side of the flexiblecircuit sheet 21 are connected via the through holes 36C to 34common-side common buses 41. The segment-side common buses 40 and thecommon-side common buses 41 are selectively coupled for carrying out apredetermined sequence control process.

The segment-side common buses 40 are gathered into 20 buses in aconnection area 42, and the common-side common buses 41 are gatheredinto 6 control buses 44 in a connection area. The 6 control buses 44 areadded to the 20 segment-side common buses 40, and a total of 26 busesare connected to the input/output buses on the face side via the throughholes 37. The buses are gathered by short-circuiting and selectingcommon buses.

After the liquid crystal panel unit 10 and the circuit unit 20 aresuperimposed one on the other, the segment and common electrodes of theliquid crystal panel unit 10 and the segment- and common-side electrodesof the circuit unit 20 are heat-sealed so as to be electricallyconnected, thus making up the liquid crystal unit 80.

The liquid crystal panel unit 10 and the circuit unit 20 aremechanically mounted on each other lightly by a double-sided adhesivetape, a cellophane tape, an adhesive, or the like.

As shown in FIG. 7, the thin board (printed board) 60 has alock-connector 61 for connection to the electrode terminals 39 of theflexible circuit sheet 21 shown in FIG. 5, and an interface connector 62for connection to electrode terminals of an external control device. Thelock connector 61 and the interface connector 62 are connected to eachother by 26 printed wires 63 having electrodes 61a, 62a on theiropposite ends. The lock connector 61 is joined to the 26 electrodes 61aby soldering or the like, and the interface connector 62 is joined tothe 26 electrodes 62a by soldering or the like.

The thin board 60 has attachment holes 64 defined therein at suitablepositions. The thin board 60 has a thickness ranging from about 0.1 mmto 2˜3 mm. The thin board 60 may be made of a synthetic resin such asepoxy, polyester, or the like, or a composite material of such asynthetic resin and glass fibers.

The thin board 60 is placed over the liquid crystal unit 80, thusproviding the liquid crystal module 1. The thin board 60 serves as areinforcing plate for the liquid crystal unit 80.

Between the thin board 60 and the liquid crystal unit 80, there isinterposed a frame-shaped spacer 70 for averaging the thicknesses of theliquid crystal unit 80. The thin board 60 and the liquid crystal unit 80are mounted on each other lightly by a double-sided adhesive tape, acellophane tape, an adhesive, or the like.

The lock connector 61 on the thin board 60 is electrically connected tothe terminals 39 on the flexible circuit sheet 21.

The lock connector 61 can freely be inserted into the terminals 39, andcan be locked in place by a lever for reliable electric connection withthe terminals 39. The lock connector 61 can freely be released from theterminals 39 by the lever without large forces. When a defect occursafter the liquid crystal panel has been mounted, the liquid crystalpanel and the flexible circuit sheet can be replaced so that the othercomponents than the liquid crystal unit can simply be reused, resultingin an increased yield.

FIG. 8 shown in plan an entire wiring system of the liquid crystalmodule. The segment electrodes are shown on the upper end, and thecommon electrodes on the righthand end.

When the liquid crystal panel 11 is viewed in front elevation, thelefthand upper end serves as the origin of a display coordinate systemon the liquid crystal panel as a display. The common electrode C₁ on thefirst row and the segment electrode S₁ on the first column arepositioned at the righthand upper end or corner as viewed from thereverse side. Similarly, the pairs of the common electrode C₁ and thesegment electrode S₂₈₈, the common electrode C₉₆ and the segmentelectrode S₁, and the common electrode C₉₆ and the segment electrodeS₂₈₈ are positioned at other ends or corners, with all the electrodesbeing given full-scale coordinates.

When a suitable control signal is applied from the external controldevice to the liquid crystal module through the interface connector 62,the control signal is applied through the printed wires 63 and the lockconnector 61 on the thin board 60 to the TAB·LSI assemblies 50A˜50C onthe flexible circuit sheet 21. The TAB·LSI assemblies 50A˜50C produceoutput signals to apply liquid crystal drive voltages to the segmentelectrodes S₁ ˜S₂₈₈, the common electrodes C₁ ˜C₉₆ of the liquid crystalpanel 11.

Since the liquid crystal module according to the present invention isflexible, ultralightweight, and ultrathin, it can be used as a singlelayer, or a plurality of liquid crystal modules can be superimposed aslayers for displaying images in multiple gradations. When the liquidcrystal module is combined with color filters, it can display colorimages easily.

The numbers of segment and common electrodes of the liquid crystal panelin the liquid crystal module may be selected as desired, and the printedwires and the number of TAB·LSI assemblies on the flexible circuit sheetare designed depending on the selected numbers of segment and commonelectrodes.

The lock connector and the interface connector may be replaced withother connectors having equivalent functions.

A second embodiment of the present invention will be described belowwith reference to FIGS. 9 through 15.

FIG. 9(a) shows in perspective view one specific arrangement of a liquidcrystal module according to the second embodiment of the presentinvention, and FIGS. 9(b) and 9(c) are cross-sectional views taken alonglines 9b--9b and 9c--9c, respectively, of FIG. 9(a), showing connectionstructures for segment and common electrode sides, respectively.

In FIGS. 9 (a) , 9 (b) , and 9 (c) , the liquid crystal module comprisesat least a liquid crystal panel 11, and TAB·LSI assemblies 50.

The liquid crystal panel 11 is composed of a liquid crystal material 110sandwiched between two flexible plastic substrates 111a, 111b. Each ofthe flexible plastic substrates 111a, 111b has a group of liquid crystaldriver electrodes 112 on its surface sandwiching the liquid crystal. Theliquid crystal driver electrodes 112 include segment electrodes 112a onthe flexible plastic substrate 111a and common electrodes 112b on theflexible plastic substrate 111b.

The materials of the flexible plastic substrates 111a, 111b and theliquid crystal 110 are the same as those of the first embodimentdescribed above.

As shown in FIG. 10, each of the liquid crystal driver TAB·LSIassemblies is similar to the liquid crystal driver TAB·LSI assemblyaccording to the first embodiment as shown in FIG. 4, except that nosprocket holes are defined. In the second embodiment, output terminals53a on a base film 51 of the TAB·LSI assembly 50 are directly connectedto the liquid crystal driver electrodes 112 on each of the flexibleplastic substrates of the liquid crystal panel 11.

The liquid crystal driver electrodes 112 (the segment electrodes 112aand the common electrodes 112b) are connected to the output terminals53a of the TAB·LSI assembly 50 by either coating an anisotropicconductive resin (hot-melt resin) 113 on the electrodes 112a, 112b andheat-sealing it with a heating head or the like to connect the liquidcrystal driver electrodes 112 and the output terminals 53a, as shown inFIGS. 9(b) and 9(c), or interposing an anisotropic conductive filmbetween the liquid crystal driver electrodes 112 and the outputterminals 53a and connecting them by way of thermal compression.

Other components of the above specific arrangement according to thesecond embodiment are not limited to any specific structures.

In the liquid crystal module of the above construction, since the basefilms of the flexible plastic substrates and the TAB·LSI assembliescomprise resin film sheets and have close coefficients of thermalexpansion, any residual stresses after they are bonded to each other aresmall enough not to cause defects such as wire breaks or panel peeling.

Another specific arrangement according to the second embodiment will bedescribed below.

FIG. 11 (a) shows in plan a liquid crystal module according to the otherspecific arrangement, and FIGS. 11(b) and 11(c) are cross-sectionalviews taken along lines 11b--11b and 11c--11c, respectively, of FIG. 11(a) .

In FIGS. 11 (a) , 11 (b) , and 11 (c) , the liquid crystal modulecomprises at least a liquid crystal panel 11, TAB·LSI assemblies 50, anda flexible circuit sheet 21.

The liquid crystal panel 11 and the TAB·LSI assemblies 50 are identicalto those in the above specific arrangement.

According to the other specific arrangement, the liquid crystal driverelectrodes 112 (the segment electrodes 112a and the common electrodes112b) on the flexible plastic substrates of the liquid crystal panel 11are connected to the output terminals 53a on the base film 51 of theTAB·LSI assembly 50 through the flexible circuit sheet 21.

The flexible circuit sheet 21 comprises a thin film (sheet) with printedwires 32 thereon, and is mounted on the reverse side of the liquidcrystal panel lightly by a double-sided adhesive tape, a cellophanetape, an adhesive, or the like.

The materials of the flexible circuit sheet 21 and the printed wires 32are the same as those of the first embodiment described above.

The printed wires may be produced by screen printing, photolithography,or the like. Hot-melt resin layers are coated as adhesive layers on theprinted wires, so that the printed wires can be connected to the outputterminals 53a of the TAB·LSI assemblies 50 by thermal compression.Components with such connecting capability are called heat-sealingconnectors.

The configuration of the film of the flexible circuit sheet 21 and thedesign of the printed wires are selected so as to be suitable forconnection between the liquid crystal driver electrodes 112 and theoutput terminals 53a on the base film 51 of the TAB·LSI assemblies 50(provided independently for driving the common and segment electrodes).

Printed wires 32 and the liquid crystal driver electrodes 112, andprinted wires 32 and the output terminals 53a of the TAB·LSI assemblies50 on the flexible circuit sheet 21 are connected to each other bysuperimposing the printed wires 32 and the electrodes 112 and the outputterminals 53a, and then joining them by way of thermal compression.

Other components of the above specific arrangement are not limited toany specific structures.

For example, a control circuit for controlling the liquid crystal driverLSI circuits is connected to the input terminals of the TAB·LSIassemblies.

The control circuit is a circuit for supplying the TAB·LSI assemblieswith signals for controlling the voltage and pulse duration of a drivesignal to be applied from the TAB·LSI assemblies to the liquid crystalpanel, and comprises a computer (CPU) or the like.

The input terminals (control terminals) 53b of the TAB·LSI assemblies 50are connected to the control circuit as follows: As shown in FIG. 11,ends of printed wires 140 on the flexible circuit sheet 21 are connectedto the input terminals 53b of the TAB·LSI assemblies 50, and the otherends of the printed wires 140 are gathered and connected to a sheet-likeconnector 141, to which the control circuit is connected. The flexiblecircuit sheet may be a board generally referred to as a flexible printedcircuit board (FPC).

As shown in FIGS. 11(b), 11(c), and 12, the liquid crystal panel 11 isusually combined with polarizing filters 12, 13, a reflector 14, or abacklight.

As in the first embodiment, the polarizing filters 12, 13 are generallymade of a polyvinyl alcohol (PVA)--iodine material, or a PVA--dyematerial. The polarizing filters 12, 13 should preferably be flexible,and hence should preferably of a thickness of 0.2 mm or less.

For display in an operation mode based on interference betweenbirefringent lights, the polarizing filters 12, 13 are disposed on theface and reverse sides, respectively, of the liquid crystal panel 11 incrossed nicols. For display in an operation mode based on a guest-hostconfiguration, the polarizing filters are disposed only on the face side(display side) of the liquid crystal, or the reverse side thereof. Inany case, the polarizing filters 12, 13 are bonded to the flexibleplastic substrates such that the contrast ratio is maximum.

The reflector 14 is identical to that according to the first embodimentdescribed above.

If a backlight is employed in place of the reflector, then the liquidcrystal panel is of the transmission type.

According to the second embodiment, the liquid crystal panel may beconstructed such that the entire structure in which the polarizingfilters and the reflector are disposed on the flexible plasticsubstrates and the liquid crystal driver circuit composed of the TAB·LSIassemblies and the flexible circuit sheet is attached to the reverseside of the liquid crystal panel, has a thickness of 3 mm or less.

As shown in FIG. 13, the liquid crystal panel is housed in a frame 114,making up a liquid crystal module which is connected to an externalcontrol circuit 150 by a cable 151. The cable 151 has a connector 141that may be fixed to the frame 114 by an adhesive, an adhesive tape, ora screw which may be selected depending on the application in which theliquid crystal module is used.

The control circuit 150 applies signals for controlling the voltage andpulse duration of a drive signal for driving the liquid crystal panel,to the TAB·LSI assemblies 50, which then drive the liquid crystal panel11.

With the polarizing filters and the reflector being disposed on theliquid crystal panel (flexible plastic substrates) and also with theliquid crystal driver circuit composed of the TAB·LSI assemblies and theflexible circuit sheet being attached (the entire thickness shouldpreferably be 3 mm or less), the liquid crystal panel can be bent in itsentirety to small and large curvatures. For example, the liquid crystalpanel may be bent into a wavy shape as shown in FIG. 14(a) , or may beheld flatwise to display images flatwise as shown in FIG. 14(b).

When the liquid crystal panel is bent, it does not suffer defects suchas wire breaks or peeling of the panel.

The liquid crystal module shown in FIG. 11 has two TAB·LSI assemblies.However, the number of connected TAB·LSI assemblies is determineddepending on the numbers of common and segment electrodes. For example,a liquid crystal panel having a display capability of 5 rows and 10columns with one character represented by 32×32 dots requires 160 commonelectrodes and 350 segment electrodes. In the case where an LSI circuithaving 160 output terminals per chip is used on each of the TAB·LSIassemblies 50 for driving a liquid crystal panel, one TAB·LSI assembly50 is connected to common-side electrode terminals and two TAB·LSIassemblies 50 are connected to segment-side electrode terminals, asshown in FIGS. 15(a)˜15(c), thus driving the liquid crystal panel with160×320 dots.

As shown in FIGS. 15(b) and 15(c), the flexible circuit sheet 21 may notbe bonded to the reverse side of the liquid crystal panel 11.

EXAMPLES

The second embodiment of the present invention will be described ingreater detail with reference to Examples.

Inventive Example 1 (the one specific arrangement)

In the liquid crystal module shown in FIGS. 9(a), 9(b), and 9(c), a filmof polyether sulfone (PES) having a thickness of 100 μm was used as eachof the flexible plastic boards, and a film of pyromellitic dianhydridepolyimide having a thickness of 100 μm (manufactured by Du Pont Ltd.;Kapton) as the base film of the TAB·LSI assemblies. The liquid crystaldriver electrodes on the flexible plastic substrates and the outputterminals on the base film of the TAB·LSI assemblies were bonded by ananisotropic conductive resin (manufactured by Three Bond Co.; Three Bond3370).

The coefficients of thermal expansion of the PES film and the base filmof the TAB·LSI assemblies were measured. The coefficient of thermalexpansion (α_(PES)) of the PES film was 5.5×10⁻⁵ (cm/cm/°C.), and thecoefficient of thermal expansion (α_(TAB)) of the base film of theTAB·LSI assemblies was 2.6×10⁻⁵ (cm/cm/°C.). The residual stress of thejoint, which was calculated from the strains that the PES film and thebase film of the TAB·LSI assemblies suffered, was 5.1×10⁻³ (Kg/cm²).These results are shown in Table 1 below.

Inventive Example 2 (the other specific arrangement)

In the liquid crystal module shown in FIGS. 11(a), 11(b), and 11(c), afilm of polyethylene terephthalate (PET) having a thickness of 50 μm wasused as the flexible circuit sheet, and the same materials as thosedescribed in Example 1 were used as the flexible plastic substrates, thebase film of the TAB·LSI assemblies, and the anisotropic conductiveresin.

The measured coefficient of thermal expansion (α_(PET)) of the PET sheetwas 7.5×10⁻⁵ (cm/cm/°C.). The residual stress of the joint between theliquid crystal driver electrodes on the flexible plastic substrates andthe connection lines on the flexible circuit sheet was 3.0×10⁻³(Kg/cm²). These results are shown in Table 1 below.

Comparative Example 1

A liquid crystal module was fabricated in the same manner as InventiveExample 1 except that glass substrates were used instead of the flexibleplastic substrates.

The measured coefficient of thermal expansion (α_(glass)) of the glasssubstrates was 3.2×10⁻⁶ (cm/cm/°C.). The measured residual stress of thejoint was 8.3×10⁻³ (Kg/cm²). These results are shown in Table 1 below.

Comparative Example 2

A liquid crystal module was fabricated in the same manner as InventiveExample 2 except that glass substrates were used instead of the flexibleplastic substrates.

The measured coefficient of thermal expansion (α_(glass)) of the glasssubstrates was 3.2×10⁻⁶ (cm/cm/°C.). The measured residual stress of thejoint was 3.2×10⁻² (Kg/cm²). These results are shown in Table 1 below.

                  TABLE 1                                                         ______________________________________                                                  Substrate                                                                            Joined      Residual stress                                            material                                                                             material    (Kg/cm.sup.2)                                    ______________________________________                                        Inventive   PES      Polyimide   5.1 × 10.sup.-3                        Example 1                                                                     Inventive   "        PET         3.0 × 10.sup.-3                        Example 2                                                                     Comparative Glass    Polyimide   8.3 × 10.sup.-3                        Example 1                                                                     Comparative "        PET         3.2 × 10.sup.-2                        Example 2                                                                     ______________________________________                                    

As is apparent from Table 1, the residual stress in the joint of theliquid crystal module according to the present invention is reduced.

Inventive Example 3

In the liquid crystal module shown in FIGS. 9(a), 9(b), and 9(c), a filmof polyether sulfone (PES) having a thickness of 100 μm was used as eachof the flexible plastic substrates, and stripe-like ITO electrodeshaving a thickness of 1000 Å were formed on the PES films. The surfacesof the PES films with the electrodes formed thereon are disposed infacing relationship to each other such that the electrodes were arrangedin a matrix, and a ferroelectric liquid crystal was sealed between thepair of these upper and lower PES films. The liquid crystal layer had athickness of about 2 μm. The sandwiched ferroelectric liquid crystal wasoriented by a known orienting process (such as disclosed in Japaneselaid-open patent publication No. 2-73219).

Then, polarizing filters (manufactured by Sanritz K.K.) each having athickness of 180 μm were bonded to upper and lower surfaces of theliquid crystal panel in a manner to provide a maximum contrast.Furthermore, a reflector (manufactured by Panac K.K.; Alpet) having athickness of about 130 μm was bonded to the lower surface of theassembly.

A flexible circuit sheet was fabricated by forming printed wires on apolyester film having a thickness of 25 μm according to a screenprinting process, and depositing a hot-melt resin layer on the printedwires. The overall thickness of the flexible circuit sheet was 40 μm.

TAB (HD66107T12) manufactured by Hitachi, Ltd. was used as the liquidcrystal driver LSI circuits. The base film was made of Kapton and had anoverall thickness of 1 mm.

One side of the flexible circuit sheet was connected to the liquidcrystal driver electrodes (common electrodes and segment electrodes) bythermal compression, and the other side of the flexible circuit sheetwas connected to the output terminals of the TAB·LSI assemblies bythermal compression. To the input terminals of the TAB·LSI assemblies,there was connected one end of another flexible sheet identical to theabove flexible circuit sheet, the other flexible sheet being connectedto a control circuit through a connector on the other end of the otherflexible circuit sheet, thus making up a liquid crystal module.

The liquid crystal panel had an overall thickness of about 1.7 mm, andcould freely be bent with the TAB·LSI assemblies (driver circuits)mounted on the reverse side thereof. It was possible to display an imageon the bent panel when image data, control data, and power were suppliedfrom the control circuit to the liquid crystal panel.

Inventive Example 4

A liquid crystal module was fabricated in the same manner as InventiveExample 3 except that a guest-host ferroelectric liquid crystalcomposition with a dye mixed therein was used as the ferroelectricliquid crystal composition, and that a polarizer was attached to onlythe display surface for a maximum contrast. The overall thickness of thepanel was about 1.5 mm.

The panel could freely be bent, and could display an image while beingbent.

Industrial applicability

The liquid crystal module according to the present invention can be usedas an information display device such as for office automation systems,home-use electric appliances, and various instruments. Particularly, theliquid crystal module is suitable for use as an information displaydevice which is required to be flexible, lightweight, and thin or low inprofile.

We claim:
 1. A liquid crystal module comprising:a matrix liquid crystalunit including a liquid crystal panel composed of two flexible plasticsubstrates and a liquid crystal material sandwiched between the flexibleplastic substrates, said liquid crystal panel having liquid crystaldrive electrodes and first terminals for the liquid crystal driveelectrodes at a side portion thereof, and a flexible circuit sheethaving a plurality of liquid crystal drive TAB·LSI assemblies mountedthereon and second and third terminals for the liquid crystal driveTAB·LSI assemblies at side portions thereof, said liquid crystal paneland said flexible circuit sheet being piled and lightly connectedtogether, and the first and second terminals being electricallyconnected to each other at the side portions; and a thin board having acircuit thereon and a lock connector at a side portion, said thin boardbeing disposed over the flexible circuit sheet and lightly connectedthereto, said lock connector being fixed to the third terminals forelectrically connecting said circuit of the thin board to the liquidcrystal drive TAB·LSI of the flexible circuit sheet so that the liquidcrystal module is made flexible.
 2. A liquid crystal module according toclaim 1, wherein said thin board doubles as a reinforcing plate for saidmatrix liquid crystal unit.
 3. A liquid crystal module according toclaim 1, wherein said liquid crystal material consists of a compositionthat comprises a ferroelectric liquid crystalline polymer.
 4. A liquidcrystal module according to claim 1, wherein said flexible circuit sheetwith the liquid crystal driver TAB·LSI assemblies mounted thereon isdisposed on a back side of said liquid crystal panel.
 5. A liquidcrystal module according to claim 1, further comprising resilientadhesive materials situated between said liquid crystal panel and saidflexible circuit sheet, and between said flexible circuit sheet and saidthin board to connect these members together.
 6. A liquid crystal modulecomprising at least a liquid crystal panel having two flexible plasticsubstrates and a liquid crystal material sandwiched between the flexibleplastic substrates, at least one of said flexible plastic substrateshaving a group of liquid crystal driver electrodes thereon and firstterminals for the liquid crystal driver electrodes at a side portionthereof,a plurality of liquid crystal driver TAB·LSI assemblies, eachhaving output terminals, and a flexible circuit sheet piled over theliquid crystal panel and lightly connected thereto, said flexiblecircuit sheet having printed wires formed thereon to which said liquidcrystal driver TAB·LSI assemblies are fixed, and second terminalslocated at ends of the printed wires at a side portion of the flexiblecircuit sheet, said first and second terminals being directly connectedtogether at the side portions to connect said liquid crystal driverTAB·LSI assemblies to said liquid crystal driver electrodes through saidconnection lines on said flexible circuit sheet so that the liquidcrystal module is made flexible.
 7. A liquid crystal module according toclaim 6, further including a polarizing filter disposed on at least oneof said two flexible plastic substrates, and a reflector disposed on anon-display side of said liquid crystal panel, wherein each of saidflexible plastic substrates have a thickness of 0.3 mm or less, saidpolarizing filter has a thickness of 0.2 mm or less, said reflector hasa thickness of 0.2 mm or less, and said flexible circuit sheet has athickness of 0.1 mm or less.
 8. A liquid crystal module according toclaim 6, wherein each of said liquid crystal drive TAB·LSI assemblieshas a group of input terminals to be connected to a control circuit forcontrolling the liquid crystal driver TAB·LSI assemblies.
 9. A liquidcrystal module according to claim 6, wherein said liquid crystal driverTAB·LSI assemblies are disposed on a back side of said liquid crystalpanel.
 10. A liquid crystal module according to claim 6, furthercomprising a resilient adhesive material situated between said liquidcrystal panel and said flexible circuit sheet to connect these memberstogether.